Within the tradition of ‘civil society tribunals’, the World Tribunal on Iraq (WTI) was an unprecedented endeavour in global scale, scope, structure and sophistication. Embedded within the global antiwar movement from 2003 to 2005, the WTI's praxis is provocative on several counts. While addressing the entanglement of cosmopolitan human rights ideals with imperial politics, this essay reflects on competing grammars of justice and legitimacy imagined by WTI activists in response to the occupation of Iraq. It also critiques what I call the instrumentalization thesis of human rights. Promulgators of this thesis typically posit that agents pursuing a distinctly imperial project are insincerely mobilizing cosmopolitan human rights ideals. Further, in order to enquire into cosmopolitan politics occasioned by the war in Iraq, and to magnify its tensions, the essay focuses on particular dilemmas faced by WTI activists while mobilizing several theorists and jurists of (cosmopolitan) democracy and (global) justice in this action. In particular, the essay interprets the ultimate controversy within the WTI network occasioned by Amnesty International's 2005 campaign for a ‘human rights based constitution in Iraq’, as well as disagreements on the ‘sources’ of the WTI's own legitimacy at its founding meeting. These debates and disagreements, the essay argues, evidence cosmopolitical tensions between the human and the citizen, between universal principles and constituted autonomies of decision, between universal and national paradigms of justice. Among the questions the essay raises are the following. How can one distinguish the cosmopolitan ethos of concern and responsibility predicating the legitimacy of the WTI, from the cosmopolitan ethos which conferred legitimacy, ex ante or ex post facto, to the constitution of a liberated, ‘democratic’ Iraq? On the threshold between the legal and the legitimate, the rule and the exception, what is the foundation, if any, of human rights politics?